BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Arctostaphylos glauca | Bigberry Manzanita 



GENERAL BOTANICAL CHARACTERISTICS : 
Bigberry manzanita is a native, evergreen, sclerophyllous shrub 3.3 to
19.8 feet (1-6 m) in height [39].  In coastal regions plants are
upright, sometimes arborescent, with a rounded to irregular crown.  Both
varieties display this growth form.  On desert borders plants are low,
compact, and spreading; this is the habit of A. glauca forma eremicola
[39,52].  Bigberry manzanita is distinguished from other manzanitas by
its large, viscid fruits containing three to six nutlets fused to form a
single large stone [26,52].  Unlike some manzanitas, this species does
not have a lignotuber [23].  It is shallow-rooted [36].  The root habit
is radially spreading, with coarse lateral roots exceeding the length of
vertical roots [33].  Bigberry manzanita can live more than 100 years
[30].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual:  Bigberry manzanita begins abundant sexual reproduction at
approximately age 20 [19].  Fifty-nine percent of filled seed collected
at widely separated locations was viable [31].  Fruit and seed
production increases with age.  Keeley and Keeley [29] found that
90-year-old bigberry manzanita stands in San Diego County yielded over
15 times more fruits than did 23-year-old stands.

Soil-stored propagules* germinate following fire scarification of the
stone [38].  One propagule usually outcompetes the others, resulting in
establishment of one seedling per seed.  Seedlings do not compete well
with annuals or sprouting species [8,30] but generally establish in
greater numbers than other obligate seeders.  Its large seed apparently
gives this species a competitive advantage over other obligate seeders
[30].  Seedling mortality is high:  most seedlings are outcompeted or
die from summer drought.  Surviving seedlings grow rapidly, and
mortality of adult plants is extremely low until the next fire [13].

*Since several bigberry manzanita nutlets are fused into a single stone,
some ecologists refer to the stones as "seed" and the individual nutlets
as "propagules" [26].  The terms "seed" and "propagule" will be so used
in this paper.

Vegetative:  Bigberry manzanita can reproduce by layering, although
plants in coastal populations rarely do so because of their upright
growth form [1,52].  Decumbent, desert-edge populations, however,
reproduce primarily by layering; sexual reproduction in these
populations is sparse [52].

Bigberry manzanita will grow epicormic sprouts following minor stem
damage [43].


SITE CHARACTERISTICS : 
Bigberry manzanita grows in a mediterranean-type climate, with hot, dry
summers and wet, mild winters.  Santa Ana foehn winds blow over
mountains from deserts in late summer and fall [15,40].  Bigberry
manzanita grows in soils derived from granite, limestone, quartz
diorite, or serpentine and that range in texture from sandy loam with
considerable coarse fragment to loam [11,16,17,21,41,46].  Bigberry
manzanita has no statistically significant association with aspect or
degree of slope [13].  Populations in the Sierra San Pedro Martir are
restricted to sites bordering water courses [37].  Bigberry manzanita
grows at elevations below 4,500 feet (1,372 m) [39].
 


SUCCESSIONAL STATUS : 
Facultative Seral Species

Bigberry manzanita colonizes from seed in postfire plant communities and
remains a component of the community through climax [13].


SEASONAL DEVELOPMENT : 
Flora primordia develop in late spring of the year prior to flowering.
Bigberry manzanita flowers from mid-February to mid-March in chaparral
and from mid-February to early April in pinyon-juniper woodlands.
Plants flower sporadically after these times, but later flowers do not
set fruit.  Fruit ripens from late February to mid-May in chaparral and
from late February through May in pinyon-juniper woodlands.  Seeds are
dispersed in late summer.  Germination occurs from mid-March to
mid-April following fire scarification of seed [1,9,26,52].

Related categories for Species: Arctostaphylos glauca | Bigberry Manzanita